1. Field of the Invention
The present invention relates to a paper making screen plate, and more specifically, to a paper making screen plate which makes use of gaps as slits, the gaps being defined by longitudinal members disposing in parallel with each other.
2. Description of the Related Art
The applicant discloses a paper making screen plate having gaps defined by longitudinal members (bar-shaped members) disposed near to each other in Japanese Patent Publication Laid-Open No. 6(1994)-299490.
The paper making screen plate disclosed in the publication includes longitudinal members (bar-shaped members) each having a circular cross section, a first support member having receiving portions for the longitudinal members (the bar-shaped members) which are annularly formed thereto at intervals and a second support member having receiving portions for the longitudinal members (the bar-shaped members) which are annularly formed thereto at intervals. The ends of the longitudinal members (the bar-shaped members) on one side of the screen plate are abutted against the receiving portions of the first support member, the ends of the longitudinal members (the bar-shaped members) on the other side are abutted against the receiving portions of the second support member, respectively, and the abutted portions are fixed by welding.
When the longitudinal members (bar-shaped members) are made to a relatively long size,. since the rigidity of the longitudinal members (bar-shaped members) cannot be kept only by the first support member and the second support member, a third support member is disposed at a suitable location of the bar-shaped members and fixed thereto by welding.
In the aforesaid paper making screen plate, since the ends of the longitudinal members (the bar-shaped members) on one side of the screen plate are abutted against the receiving portions of the first support member, the ends of the longitudinal members (the bar-shaped members) on the other side are abutted against the receiving portions of the second support member and the abutted portions are fixed by welding, the longitudinal members (bar-shaped members) are deformed by thermal stress and the like.
Moreover, since the longitudinal members (bar-shaped members) are fixed to the third support member by welding at the intermediate portions thereof, a problem arises in that an amount of deformation is further increased and the gaps defined between the longitudinal members (bar-shaped members) cannot be kept constant and thus the performance of the screen plate is lowered.
In addition, there is also a problem that when one of the longitudinal members (bar-shaped members) is damaged in the state that the screen plate is used by being assembled to a screen, since the longitudinal member (bar-shaped member) is fixed by welding in the intermediate portion thereof, it is very time-consuming to replace the damaged longitudinal member (bar-shaped member).
An object of the present invention is to provide a paper making screen plate arranged to remove the aforesaid conventional problems.